Composition comprising reaction product of hydrolyzed vinyl acetate polymer and periodate oxidized polysaccharide and process for preparing same

ABSTRACT

Reaction products of polymers of vinyl acetate and dialdehyde polysaccharides may be prepared by mixing emulsions of vinyl acetate polymers with aqueous dispersions of dialdehyde polysaccharides at a pH of 4 to 6.  The vinyl acetate polymer may be polyvinyl acetate or a copolymer of vinyl acetate with vinyl propionate, vinyl 2-ethylhexoate, vinyl chloride, vinyl maleates, vinyl fumarates, acrylic esters or acrylonitrile, and may be partially hydrolysed, e.g. to contain 2 to 80% of polyvinyl alcohol.  A plasticizer, e.g. acetyl triethylcitrate, and protective colloids, e.g. methyl cellulose, sodium carboxymethyl cellulose, hydroxyethyl cellulose, sodium and ammonium polyacrylates, polyvinyl alcohol, alginates and starches, may also be incorporated.  The dialdehyde polysaccharide may be prepared by oxidizing starch, cellulose, dextrins and dextrans with periodic acid, and the aqueous dispersion thereof may be prepared by heating a slurry thereof in the presence of a buffer, e.g. sodium acetate, sodium bicarbonate or disodium phosphate.  The products are less water-sensitive than the polymers from which they are prepared, and may be used in coating, making films, as binders for non-woven fabrics and in the paper industry.

United States Patent M 3,098,049 COMPOSITION COMPRISING REACTION PROD- UCT OF HYDROLYZED VINYL ACETATE POLY- MER AND PERIODATE OXIDIZED POLYSAC- gAMHARmE E AND PROCESS FOR PREPARING Peter J. Bor-chert, Elkhart, Ind., assignor to Miles Laboratories, Inc., Elkhart, Ind., a corporation of Indiana No Drawing. Filed Apr. 13, 1960, Ser. No. 21,895 8 Claims. (Cl. 260-174) This invention relates to polymeric compositions derived from polymers of vinyl acetate and dialdehyde polysaccharides. In one of its more particular aspects this invention relates to films formed from the interaction of polymers of vinyl acetate and dialdehyde polysaccharides.

Polyvinyl acetate and its copolymers in the form of aqueous emulsions are used as vehicles for emulsion paints, particularly paints used on stucco and concrete. They also have utility in plaster and dry-wall construction as primer sealers. In addition they find use in the textile industry in the formulation of semi-transparent finishes and as binders for non-woven fabrics and in the paper industry for their greaseproof and waterproof coating characteristics.

It is a well known fact that plastic films formed from aqueous emulsions of polyvinyl acetate and some of its copolymers have a tendency to swell, soften and reemulsify upon contact with water. Complete destruction of the film takes place within a relatively short period of time depending upon such conditions as film thickness, drying conditions and immersion temperature. For many of the uses to which emulsions of these polymers are put a more effective water, scrub and soap resistance and a shorter film drying time is desirable.

It is accordingly a principal object of this invention to provide polymeric compositions which have the desirable properties of polyvinyl acetate film-formers and in which the undesirable properties of these polymers are not present.

Another object of this invention is to provide compositions which may be used to form films having improved water resistance.

Another object of this invention is to provide films of superior exterior durability.

A further object of this invention is to provide a method for the preparation of compositions having the aforesaid desirable properties.

Other objects and advantages of this invention will become apparent in the course of the following detailed disclosure and description.

It has now been found that compositions having the already desirable properties of polymers of vinyl acetate and improved properties with respect to water resistance and durability may be prepared by the interaction of polymers of vinyl acetate with dialdehyde polysaccharides. The resulting compositions are characterized by forming films which are stable not only upon contact with water but even under more severe solvent treatment.

The vinyl acetate polymers which may be used in the novel compositions of this invention may be homo-polymers of vinyl acetate or copolymers prepared by the copolymerization of vinyl acetate with various comonomers copolymerizable therewith. For example, such comono-I i mers as vinyl propionate, vinyl Z-ethylhexoate, vinyl chloride, vinyl maleates, vinyl fumarates, various acrylates andacrylonitriles aslwell as the higher vinyl esters may be 3,098,049 Patented July 16,1963

available, as externally plasticized polyvinyl acetate emulsions, or as copoly-mcr emulsions in which the comonomer copolymerized with the vinyl acetate is a flexibility imparting monomer which provides permanent flexibility without the use of added plasticizers. There are also available for use polyvinyl acetate powders which may be dispersed in Water to form aqueous emulsions.

It will be understood in the art that some hydrolysis both of the vinyl acetate or other ester monomers and of the polyvinyl acetates occurs during polymerization. The degree of hydrolysis of polyvinyl acetate in standard finished emulsions is usually in the range of about 0.1% to 2%. The use of such partially hydrolyzed polyvinyl acetates and those wherein hydrolysis is accomplished after polymerization, wherein the hydroxyl content, expressed as percent of polyvinyl alcohol, is from about 2% to is included within the concept of this invention. In fact, it is believed that the excellent water resistance or Water insensitivity of the compositions of this invention is due in part to the utilization of the hydroxyl groups resulting from partial hydrolysis of the polyvinyl acetates. Cross-linkages are formed between chains of the vinyl alcohol fractions of the polyvinyl acetates and the dialdehyde polysaccharides.

The dialdehyde polysaccharides which interact with the polyvinyl acetates to form the novel compositions of this invention are those obtained by the oxidation of polymeric polysaccharides such as by the action of peri odic acid. This well known reaction may be exemplified by the oxidation of starches with periodic acid in accordance with the equation shown below:

It may be seen that the resulting product of this oxidation, known in the art is dialdehyde starch, is a polymer which contains two aldehyde groups per glycoside unit of the starch molecule resulting from oxidation of the corresponding l,2-glycol. Other polysaccharides than starches may be utilized in the preparation of the polymeric dialdehydes, for example, celluloses, dextrins, dextrans and the like. It will be appreciated that dialdehyde starch and other dialdehyde polysaccharides may exist with varying degrees of oxidation depending upon the conditions under which the oxidation reaction is carried out. For the purpose of this invention, in order to prepare films having the greatest degree of water insensitivity, it is preferred that a highly oxidized dialdehyde starch be used, for example, one comprising a starch which has been about oxidized. By a 90% oxidized starch is meant one in which 90 out of every glycoside units have been converted to the dialdehyde. Other levels of oxidation may, of course, be utilized if desired.

Dialdehyde starch may be advantageously prepared for use in the form of an aqueous dispersion by heating a slurry of the dialdehyde starch until a homogeneous dispersion of dialdehyde starch is obtained. Heating with a 0.1 N t o' 1.0 'N'solution of a buffer salt such as sodium acetate, sodium bicarbonate, disodium phosphate or the like, at a temperature of 40 C. to 50 C. aids the stadispersions may then be utilized for preparing the novel compositions of this invention without further treatment.

4 position which may be characterized as having the following structure:

If the polyvinyl acetate is to be used as a dispersible H, CH powder then the dialdehyde polysaccharide may also be :0 (3:0 used in this form. 5 l i In the practice of the present invention the dialdehyde starch or other dialdehyde polysaccharide may be used ...CHiGH-CHi0H-CHi-0H... in an amount of from about 0.05% to about 2% based 0 on the weight of the polyvinyl acetate and preferably in H 1 the range of from about 0.5% to about 1%.

The preparation of these novel polymeric composihHCHo-i H0- tions having improved water resistance is physically ac- HFOH J complished by mixing an emulsion of the polyviny e It has been found that the dialdehyde polysaccharide is late i fhsperslon of dlaldehyde polysacchailde' not absorbed within the particles of the polyvinyl acetate. The dispersion may he Prepared for use described Instead, it is seen to remain on the surface of the polymer above If desired the dialdehyde polysflcchande may be particles together With the protective colloid. This suradded ihe Polyvinyl acetate higher temperature face treatment of the polymer particles is apparently than room temperature but elevated temperatures are responsible for the observed water resistance of the renot essential for this purpose. In fact, room temperature sulting polymeric compositions. is preferred since less degradation of the polymers oc- The invention will vbe better understood by referenoe curs at room temperature than at elevated temperatures. to the following examples which are included f purposes It is generally unnecessary the hydrogen of illustration and are not to be construed as in any way concentration of the polyvinyl acetate emulsion prior to limiting the Scope of the instant invention addition of the dialdehyde polysaccharide. These emulsions have their optimum latex stability and are supplied EXAMPLE 1 at about P 4 To P Sihee this acidic medium favors A 25% solid-containing dispersion of dialdehyde starch the cross-linking reaction between the polyvinyl acetate was prepared b ddi 50 f 90% oxidized dialdehyde and the dialdehyde polysaccharide no additional acid need Starch 10% moisture content) i 10 portions .1 135 be used to catalyze ilhe ieaeiionml. samples of tap water containing, dissolved therein, 5 It has generally been found desillahle to incorporate g. of sodium acetate. The additions were made gradually With the Polyvinyl acetate and ihe dialdehyde Starch a over a period of about 10 minutes each and the resulting protective colloid such as is used in emulsions to prevent mixture was h d i h i i at 50 C til a h agglomeration of the Polymer Particles as y are geneous dispersion of dialdehyde starch was obtained. formed, and to maintain finished P y in a stable The dialdehyde starch dispersion was diluted to form latex form. Since a protective colloid also increases the 5 10% aqueous di i d hi di i mixgd ith viscosity of th aqu Phase and thereby reduces the commercially available polyvinyl acetate emulsion consedirnentation rate of the solid particles it is also known taining 55% 1 Films were f d from the l to produce a stabilizing eflect on the emulsion. EX- i emulsion b l i i h a 11 {Q g1as5 m t d emplary of protective colloids frequently used are sodium drying b evaporation f water t room temperature (25 cafboximehhyl Cellulose, Y Y ethyl Cellulose, the C.) for 18 to 20 hours. In some cases an additional Sodium Or am o Polyaefylaies, Polyvinyl alcohol, amount of a protective colloid (methyl cellulose) or an olginaies and starches, which are commercially aveilexternal plasticizer (acetyl triethylcitrate) was also inable for this purpose. cluded. The films were then stripped oif the glass plates AS Pointed out above, the formation of hhe novel and their thickness was measured. Strips having dimen- Polymerie compositions of this invention and sions of 4 mm. by 15 mm. were cut from each sample proved water resistance thereof has been shown to be due and i d i Watgf at room temperature f one 1 m a Cross-linking reaeiioh heiWee11 the chains of P The increase in area of the strip after immersion in water Vinyl acetates oh the one hand and dialdehyde p was calculated. In addition, the stability of the films in charides on the other. The exact mechanism of the crossvarious Solvents at room temperature was Observed, I linking reaction is not known but it is likely that ihiefall cases the films took up Water within 30 to 60 minutes action between the tWO yp of P y results ill (the but remained intact and were not sticky or tacky in cases formation of acetal type cross-linkages. This acetal where dialdehyde starch was added. The results are sum formation gives rise to a relatively stable polymeric commarized in Table I.

Table 1 Area 0! film Stability of film in various Polyvinyl Dialdehyde Protective Film dryafter immersolvents Expt. acetate starch colloid Plasticizer ing time at Film thicksioninwater No. (parts by (parts by (parts by (parts by 25 0. mass (mils) (percentweight dry weight dry weight dry weight) (hours) original area 10% Non-ionic 1Nhydrobasis) basis) basis) =100%) sodium suriaoehloric chloride tani: acid 27. 5 0. 2 is 8-10 20 20 25 55 .55 20 20-25 106 55 55 i 3 is 20-25 106 =1: 27. 5 1. as 0. 2 18 8-10 106 a: 27. 6 2. 75 0. 2 18 8-10 106 :l: 55 0. 28 B 3 is 20-25 106 1 Added as 2% aqueous dispersion of methyl cellulose (Methocel HG, Dow Chemical Co.) 9 Strips were immersed in solutions as indicated and the qualities of the films evaluated as film intact, tacky; film re-emulsifies. B 1% 'iergitoi NPX, Union Carbide Corp. 4 Film re-en1ulsifles within 1 hour. 6 Acetyl triethylcitrate.

follows; film intact, not tacky; i

The following example illustrates the use of a partially hydrolyzed polyvinyl acetate in preparing the water resistant composition of this invention.

EXAMPLE 2 The procedure of Example 1 was followed except that an emulsion of a partially hydrolyzed polyvinyl acetate with a residual of 19.5-21.5 of polyvinyl acetate was combined with varying amounts of a dispersion of dialdetially unafiected by treatment with various solvents. On the other hand, films formed from polyvinyl acetates alone are seen to re-emulsify in water within a very short period of time and usually within one hour. The novel compositions of this invention, then, have been shown to have inhanced water resistance and improved stability and films formed from these compositions have been shown to be considerably more durable than films formed from polyvinyl acetate itself.

hyde starch. The results are given in Table 2. 10 In summary, this invention provides polymeric composi- Table 2 Partially Area of film Stability t film in various solvents hydrolyzed Dialdehyde Film drying after immer- Expt. polyvinyl starch (parts time at 25 0. Film thicksion in water No. acetate (parts by weight (hours) ness (mils) (percent- 10% sodium Non-ionic 1 N hydroby weight dry dry basis) original area= Chloride Surfactant chloric acid basis) 1 s 20 18 5-7 9 20 0.1 18 5-7 143 10. 20 0. 2 is 5-7 138 11 20 0. 4 18 5-7 137 1 Added as by weight aqueous dispersion.

3 200, film is slimy and falls apart.

These results indicate that a more highly hydrolyzed polyvinyl acetate produces a film which, when mixed with dialdehyde starch displays a greater area increase than in the case of the less highly hydrolyzed sample. It is to be noted that an area increase of about 200 is considered satisfactory for many applications.

The following example is included to illustrate the use of a polyvinyl acetate powder in forming the improved compositions of this invention.

EXAMPLE 3 A 10% dispersion of dialdehyde starch was prepared by adding 20 g. of 90% oxidized dialdehyde starch (10% moisture) with stirring to 162 ml. of tap water and heating the mixture at 70 C. for 20 minutes until a homogeneous dispersion was formed. A commercially available polyvinyl acetate powder was dispersed in water at 40 C. to give a resin solids content of 50% and the resulting dispersion was mixed with diiferent amounts of the 10% dialdehyde starch dispersion. The resulting polymeric compositions were applied with a roller to glass plates and evaluated as described in Example 1. The results are tions formed from the interaction of polyvinyl acetates and dialdehyde polysaccharides. These compositions are capable of forming films of greatly improved water resistance and durability.

Other embodiments than those specifically described may, of course, be used in the practice of this invention and are intended to be included within the scope thereof, which is defined in the appended claims.

What is claimed is:

l. A composition comprising the reaction product of (a) a partially hydrolyzed polymer of vinyl acetate having a hydroxyl content expressed as percent of polyvinyl alcohol of about from 2% to 80% selected from the group consisting of homopolymers of vinyl acetate and copolymers of vinyl acetate with ethylenically unsaturated monomers with (b) a periodate oxidized polysaccharide, wherein said periodate oxidized polysaccharide is present in an amount of about between 0.05% to 2% based on the weight of said polymer of vinyl acetate.

2. A composition according to claim 1 wherein the periodate oxidized polysaccharide is an oxidized polysaccharide in which the level of oxidation is about at least shown in Table 3. 90%.

Table 3 Polyvinyl Dialdehyde Area of film Stability of film in various solvents acetate powder starch I ilm drying Film after immer- Expt. (parts by (parts by time at thickness sion in water N 0. weight dry weight dry 25 C. (mils) (percentbasis) 1 basis) 2 (hours) or1gina1area= 10% Sodium N on-ionic 1 N hydro- 0 chloride surfactant chloric acid 50 18 20-25 Falls apart so 0. 5 18 20-25 114 50 1.0 is 20-25 112 Added as a 50% by weight aqueous dispersion. Added as a 10% by weight aqueous dispersion.

These results indicate that the improved compositions of this invention can be prepared by the use of commercially available polyvinyl acetate powders and that the compositions resulting from a mixture of emulsions prepared from these powders with dispersions of dialdehyde starch have greatly enhanced water stability.

It can thus be seen that the use of dialdehyde starch with polyvinyl acetate results in films which do not reemulsify upon immersion in water and which are substan- 3. A composition according to claim 1 wherein the periodate oxidized polysaccharide is periodate oxidized starch.

4. A composition according to claim 1 wherein the periodate oxidized polysaccharide is present in an amount of about between 0.5% to 1% based on the weight of said polymer of vinyl acetate.

5. A film formed upon the drying of an aqueous emulsion of the composition of claim 1.

6. A process for the preparation of a water insensitive polymeric composition which comprises reacting (a) an aqueous emulsion of a partially hydrolyzed polymer of vinyl acetate having a hydroxyl content expressed as percent of polyvinyl alcohol of about from 2% to 80% selected from the group consisting of homopolymers of vinyl acetate and copolymers of vinyl acetate with ethylenically unsaturated monomers with (b) an aqueous dispersion of a periodate oxidized polysaccharide, in a proportion of about between 0.05% to 2% of periodate oxidized polysaccharide based on the weight of said polymer of vinyl acetate at a hydrogen ion concentration of about from pH 4 to pH 6.

7. A process according to claim 6 wherein the dispersion of the periodate oxidized polysaccharide is prepared by heating a slurry composed of said periodate oxidized References Cited in the file of this patent UNITED STATES PATENTS Wright et al. Oct. 15, 1957 Wise et al. Oct. 18, 1960 OTHER REFERENCES Kerr: The Chemistry and Industry of Starch, 2nd

edition, published by Academic Press Inc., 1950, pages 328-336. 

1. A COMPOSITION COMPRISING THE REACTION PRODUCT OF (A) A PARTIALLY HYDROLYZED POLYMER OF VINYL ACETATE HAVING A HYDROXYL CONTENT EXPRESSED AS PERCENT OF POLYVINYL ALCOHOL OF ABOUT FROM 2% TO 80% SELECTED FROM THE GROUP CONSISTING OF HOMOPOLYNETS OF VINYL ACETATE AND COPOLYMERS OF VINYL ACETATE WITH ETHYLENICALLY UNSATURATED MONOMERS WWITH (B) A PERIODATE OXIDIZED POLYSACCHARIDE, WHEREIN SAID PERIODATE OXIDIZED POLYSACCHARIDE IS PRESENT IN AN AMOUNT OF ABOUT BETWEEN 0.05% TO 2% BASED ON THE WEIGHT OF SAID POLYMER OF VINYL ACETATE. 